10. The disintegration of Space Shuttle Challenger, watched live by nearly 20% of Americans, was caused by a flawed engine design that was willfully ignored by NASA engineers
On January 28, 1986, Space Shuttle Challenger embarked upon its tenth, and ultimately final flight. Just 73 seconds after takeoff the spacecraft suffered a critical disintegration, breaking apart over the Atlantic Ocean. The crew cabin, made of reinforced aluminum and housing the seven crew members, detached from the wreckage in a single piece. Entering a free fall, the cabin crashed into the ocean at approximately 207 miles per hour. It is believed that at least some of the crew were conscious throughout this descent; however, all aboard were killed instantly by the immense force of impact.
Crash investigations discovered that the right solid rocket booster had failed at liftoff, caused by joint seals that were not designed to handle the cold conditions on the day of the launch. The failure of the seal to adequately pressurize the booster triggered a breach, allowing burning gas to escape the rocket motor and ignite the external fuel tank. NASA managers had been made aware of the potentially fatal flaw in 1977, but had failed to put into place sufficient alterations and disregarded warnings concerning the threat posed by low temperatures on the morning of January 28.